(1) Field of the Invention
The present invention generally relates to compositions and treatments for vascular disorders. More specifically, the invention provides compositions comprising Fat1 or isolated domains thereof, and methods of using these and other compositions with methods of vascular repair such as angioplasty and coronary bypass surgery.
(2) Description of the Related Art
Vascular remodeling is a critical part of the pathogenesis of clinically important vascular disorders such as atherosclerosis, restenosis after angioplasty, and saphenous vein graft disease (Shanahan and Weissberg, 1998; Owens et al., 2004). Despite considerable study, the molecular mechanisms that control vascular smooth muscle cell (VSMC) activities during vascular remodeling are not fully understood. Recent reports linking cadherins to VSMC regulation (Jones et al., 2002; Slater et al., 2004; Uglow et al., 2003) suggest that these transmembrane adhesion proteins, characterized extensively as major mediators of epithelial cell homeostasis, may also be important in vascular remodeling.
Cadherins are involved in Ca2+-dependent cell-cell adhesion, intracellular junction assembly, and tissue morphogenesis during development (Yap et al., 1997; Angst et al., 2001; Wheelock and Johnson, 2003b). Major subdivisions of the large cadherin superfamily include the classical cadherins and the protocadherins (Gallin, 1998; Yagi and Takeichi, 2000; Angst et al., 2001). The extracellular domains of these proteins share a unique structure, the cadherin motif, which is repeated in tandem in variable numbers. Classical cadherins function as homophilic adhesive molecules, and both extracellular and cytoplasmic domains contribute to this function. Classical cadherin cytoplasmic domains interact with β-catenin and plakoglobin (Huber and Weis, 2001; Takeichi, 1995), members of the armadillo gene family of transcription factors. This interaction effectively sequesters β-catenin away from the nucleus, limits its transcriptional activity (Sadot et al., 1998; Kaplan et al., 2001; Simcha et al., 2001), and thus links cadherins to the canonical Wnt signaling pathway, a major determinant of cellular activity during development (Bhanot et al., 1999; Jamora et al., 2003; Nelson and Nusse, 2004).
Like classical cadherins, protocadherins have extracellular domains capable of Ca2+-dependent, homophilic interaction (Suzuki, 2000). Protocadherin cytoplasmic domains, on the other hand, are structurally divergent from those of the classical cadherins, and less is known about their function. Sequestration and inhibition of β-catenin by protocadherins has not been described.
Although mammalian Fat1 genes (Dunne et al., 1995; Ponassi et al., 1999; Cox et al., 2000) were initially characterized as homologues of the Drosophila protein Fat (Mahoney et al., 1991), recent bioinformatics analysis indicates that Fat1 is more closely related to Drosophila Fat-like (Ftl) (Castillejo-Lopez et al., 2004). In Drosophila, Ftl is expressed apically in luminal tissues such as trachea, salivary glands, proventriculus, and hindgut (Castillejo-Lopez et al., 2004). Silencing of ftl results in the collapse of tracheal epithelia, and it has been suggested that Ftl is required for morphogenesis and maintenance of tubular structures of ectodermal origin.
Like Drosophila Fat and Ftl, mammalian Fat1 is remarkable for its very large size (˜4600 aa). It has a huge extracellular domain that contains 34 cadherin repeats, 5 EGF-like repeats, and l laminin A-G motif, a single transmembrane region, and a cytoplasmic tail of ˜400 aa (Dunne et al., 1995). Sequences within the Fat1 cytoplasmic domain (Fat1IC) show limited similarity to β-catenin binding regions of classical cadherins (Dunne et al., 1995).